Electric discharge device heater



April 27, 1937.

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INVENTOR Patented Apr. 27, 1937 ELECTRIC DISCHARGE DEVICE HEATER Walter Stockmeyer, Finkenkrug, near Berlin, Germany, assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., acorporation of Pennsylvania Application July 10, 1934, Serial No. 734,486 In Germany July 17, 1933 3 Claims. (Cl. 250-275) My invention relates to electric discharge deformation and has a lead I6 connected to the coil vices and more particularly for heating means with the opposite end of the heater l2 preferably for portions of electric discharge devices containconnected to the cathode casing H which has ing a metallic vapor. the cathode leads I! and I8.

An object of the invention is to prevent back- The anode M has a supporting means or stem fire and similar discharges from the electrodes l9 and within this supporting or reentrant stem to the metallic vapor condensed upon the walls I9 are coils for heating the portion of the stem of the container. or supporting means adjacent to the anode head In metallic vapor rectifiers the metallic vapor I l. Similar coils 2| are also placed about the condenses in the cooler portions of the container portion of the casing 22 adjacent to this reenespecially the supports closely adjacent to the trant stem l9. These heating coils are preferbody of the electrodes where the temperature ablyembedded in any suitable electrical insuladuring operation is lower than the temperature tion23 protected by a cap 24. The anode lead of the electrodes. This is especially true in the also preferably passes through this insulating region surrounding the anode and the supportmaterial 23 and it is preferred to provide a heating portion for the anode. These deposits of the ing coil 25 for the anode head M. The anode metallic vapor are frequently the cause of backlead can be one of the leads 26 or 21 for this fire and creepage discharge. heating coil and the anode can be connected at According to the present invention, these difa certain place on the coil 25. ficulties are overcome by providing heating means for the supports and the parts of the casing closely adjacent to the electrodes and for the anode structure itself. The supporting members and the wall portions adjacent to the electrodes are heated to such a distance from the electrode that no creepage discharges can occur between the electrodes and these parts of the casing under ordinary operating conditions.

Other objects of my invention will become apparent upon reading the following specification and the drawing, in which Figure 1 is a longitudinal cross sectional view of a tube embodying the invention.

Fig. 2 is a similar longitudinal cross sectional view of the tube with modifications of the invention as disclosed in Fig. 1.

Fig. 3 is an enlarged cross sectional view through an anode structure in the combination of heating means therein; and

Fig. 4 is a diagram of preferred connections to the tube.

The tube disclosed in Fig. 1 has a container l0 which is normally vacuum-tight and contains a gaseous filling preferably in the form of a metallic vapor. The most common of these metallic vapors is, of course, mercury. Within the container I0 is the cathode II which is preferably in the form of a barium and strontium oxide coated surface on a container with a heater l2 enclosed within the reentrant portion I3 of said container for indirectlyheating the oxide surface. The upper portion of the cathode container II is open towards the anode l4 and may have a screen l5 across this opening, if desired. The heater I2 may, of course, be of any desired for the anode head for rectifiers of very large capacity is disclosed in Fig. 3. The anode head 30 has the coil 3| embedded therein for heating the surface to prevent a metallic vapor from condensing thereon. A similar coil 32 is provided on the supporting portion for said anode head so that no metallic vapor will be deposited on the surface of the head and the parts of the casing adjacent thereto. If desired, a cooling arrangement may be made for the lower portion of the anode head which is loaded electrically to a relatively high degree. There is, of course, no danger of the mercury or other metallic vapor being deposited on this end portion of the anode head because this portion will be entirely heated after a very short time of operation. It may be desired, however, to heat the anode when the apparatus is first connected to prevent backfire from the mercury that might be deposited from the anode.

Fig. 2 discloses a tube somewhat similar to Fig. 1 except, in this arrangement, the heating coil 35 is disclosed connected to the cathode. This heating coil has suitable connections with the leads I! and I8. The remaining portions of the interior of the casing may be similar to that disclosed in Fig. 1. In addition to or in place of the heating coils 20 and 2| of Fig. 1, a heating coil 36 in the form of an annular heater tainer adjacent to the anode and this annular heater may be connected to the cathode by the lead 37. This heater may be in place of or in addition to the annular heating coil 35 on the interior of the casing. When this annular heater A preferred construction of the heating coil may be placed around the outside of the consuch as the screen 38 for preventing undesired current leakage between the coil 36 and the cap 24, which may be connected to the anode.

A preferred method of making connections "to the tube and heating elements is disclosed in Fig. 4. The heating means 40 is preferably connected to the anode l4 and this heating means is energized by means of a transformer 4l around the circuit 42. The cathode H has the heating means or coil 43 connected thereto which is energized by a transformer 44 connected to the circuit 45. It is, of course, possible also to use heaters, part of which are connected to the anode and partof which are connected to the cathode. These coils, represented diagrammatically by 40 and 43 may be any or all of coils 20, 2|, 25, 3|, 32, 35 and 36 represented in Figs. 1, 2 and 3. The tube circuit proper is disclosed as the circuit 46 connected to the anode and cathode and including a suitable transformer 47 and resistance 48. It is, of course, apparent that this type and arrangement of the heating means will depend upon the design of the discharge device and upon the individual conditions in each case. The heating coil connected to the cathode may also advantageously be so connected that it is traversed by the heating current of the cathode, that is, it may be connected in series therewith. The circuits 42, 45 and 46 disclosed in Fig. 4 may, of course, be connected by use of suitable transformers to a single source for power purposes.

For the sake ofsimplicity, the invention has been disclosed as applied to two electrode rectifiers but it is obvious that the invention is also applicable to similar metallic vapor devices using more than these two electrodes such as the controlled rectifiers having a grid therein and also to grid controlled inverters or converters. The heating means when applied to such discharge devices may be associated also or only with the auxiliary electrodes serving to control the device. If the heating means is combined with heat storage parts, it may be possible to save fheat energy.

While I have in the foregoing described certain particular embodiments of my invention, it will be understood that these are for purposes of illustration only and that the broad principles may be otherwise utilized as will be readily apparent from those skilled in the art. I desire, therefore that the following claims shall be accorded the broadest construction of which their terms are susceptible in view of the limitations imposed by the prior art.

I claim as my invention:

1. An electric discharge device comprising a container, a cathode and an anode in said container, a metallic vapor in said container, supporting means for said anode comprising a neck extending from the inner walls of said container, and heating means within said neck and also about the adjacent container walls.

2. An electric discharge device comprising a container having a metallic vapor therein, a stem container having a metallic vapor therein, a reentrant stem projecting into said container, an anode supported on said stem, electrical insulation on the outside of said container surrounding said reentrant stem and a heater embedded in said insulation.

WALTER STOCKMEYER. 

